Salad dressings, seasoned and spiced, slightly acidic vegetable oil-water combinations, have long been used to enhance the taste appeal of raw and cooked vegetables, fruits, sliced or chopped cooked and/or cured meats, cooked fish, cheese, cooked eggs and many combinations thereof. In certain food cultures, salads with dressing are an important part of meal menus.
The so-called emulsified dressings (oil-in-water emulsions) such as mayonnaise, and mayonnaise-like salad dressings, are a substantial segment of the salad dressing market. They enjoy wide utilization. These dressings may be prepared at the point of use, but are most often produced as finished goods for retail, institutional, and food service markets. A growing use is in the production of refrigerated salads for delicatessen, restaurant, and fast food outlets.
The composition and ingredients of mayonnaise and salad dressing are specified in the Code of Federal Regulations (CFR Title 21, Part 169, Subpart B-Sections 169.140 and 169.150). Any dressing that departs from the given standard of identity cannot be called mayonnaise or salad dressing, as the case may be. There are commercially-available products which do not conform to these standards. These are merchandized as simply dressings or are given some fanciful name. In spite of their non-conformity to the cited regulations, these items are widely used and perform useful functions.
Salad dressing is further described as the emulsified semi-solid food prepared from vegetable oil(s), acidifying ingredients, vinegar and or lemon/lime juice, egg yolk or egg yolk-containing ingredients, a starchy paste, and one or more optional ingredients including: (a) salt, (b) nutritive carbohydrate sweetners, (c) spice or natural flavoring except those which impart an egg-yolk color, (d) monosodium glutamate, (e) stabilizers and thickners, (f) citric/malic acids, (g) sequestrants, and (h) crystallization inhibitors. As indicated above, there are many emulsified dressings which depart from this recipe in one or more ways. Customarily, an emulsion is made from the vegetable oil, egg yolk, water, and certain other ingredients such as vinegar and spices. This emulsion is combined with a cooked starch paste after cooling of the starch paste. The paste may contain the other spicing and flavoring ingredients.
It has been indicated in older literature discussing mayonnaise, that the challenge in making an emulsified oil-in-water dressing is to produce a product which resists "oiling-off" on storage. At one time it was not unusual to see on the retail shelf, or after home storage at room or refrigerated temperatures, a jar of dressing with a yellow oil layer at the top.
With an increasing industry recognition of the effect of the compositional and processing factors on emulsion stability, gross instability such as recited above was overcome, for the most part.
However, changing patterns of marketing, including warehousing, transportation, merchandising, and even utilization, resulted in a demand for dressings of greater stability toward stress environmental conditions. With increasing areas of distribution, the need for frozen dressings became apparent. This prompted investigation of means for the production of freeze-thaw stable dressings. The perfect model is an emulsified oil-in-water dressing which can undergo an infinite number of freezing and thawing cycles in storage, transportation, and use, and yet maintain dressing integrity. Such has not been accomplished, but the challenge remains. Some progress has been made in achieving this goal, but new, innovative technology is needed to approach such an ideal.
Buchanan and Drury, in U.S. Pat. No. 2,338,083, recognized the sensitivity of salad dressings to temperature change with separation of components which they term "weeping". They advocated the use of a waxy maize or a waxy cereal starch as a portion of the starch paste for improved stability. However, they did not address the question of freeze-thaw stability, but were, apparently, concerned with more modest changes in temperature.
Melnick, Gooding and Vahlteich, in U.S. Pat. No. 2,627,469, addressed the question of the "freeze or cold resistance" of mayonnaise. It should be noted that these inventors were concerned with emulsified dressings wherein the water was limited because of the high oil content (mayonnaise-minimum 65% vegetable oil). It has been noted that the behavior of the water during freezing of a dressing is a critical factor in stability. Further, these inventors were concerned with inadvertent freezing of the dressing such as in home refrigerators set too low, and in winter storage and transportation. They claimed that a specific vegetable oil combination resulted in a mayonnaise with marked cold resistance according to their test procedure.
Partyka, in U.S. Pat. No. 3,093,485 (issued June 11, 1963), directly addressed the question of an emulsified salad dressing which is stable under freezing conditions, and can be used in frozen foods such as salads and sandwiches.
Partyka states that the prior art indicated the need to use vegetable oils, such as cottonseed oil, that were free of "winterizable" components, that is, hard fats that separate on chilling the oil(s), for improved resistance of salad dressings to cold stress. Further, he states that the use of oils free of winterizable components have provided certain cold stability, but such does not provide a satisfactory emulsified salad dressing which resists fat separation on freezing.
The essentials of Partyka's alleged invention for an improved freeze-resistant salad dressing included a specified soft oil with winterizable components (iodine value 75 to 115) which clouds when placed in an ice bath for 5.5 hours, a freeze resistant starch to imbide all the water in the dressing and retain the water under freezing conditions, and egg yolk or yolk equivalent at a level of 8 percent of the soft oil in the edible oil.
The importance of the use of freeze-resistant starch in the preparation of the cooked starch paste is emphasized. Partyka states that such starches are known, and are commercially available. He recites such starches as sold under the tradenames, Col-Flo 67 and Freezist. He points out that such starches may be used in starch blends wherein the other starches need not retain water under freezing conditions, though the resulting starch gel or paste after cooking should be freeze resistant.
Another important statement of Partyka is "It is well known in the art that various pieces of mechanical equipment effect tighter emulsions. However, the mechanical conditions of emulsification have not been found to provide any unusual advantages in respect of the freeze stability of the emulsified salad dressing. Therefore, the selection of the particular equipment is largely a matter of choice to provide a dressing body of desired characteristics." (U.S. Pat. No. 3,093,485; column 3, lines 6-13).
The teaching of Krett in U.S. Pat. No. 3,093,486 for the production of a freeze-thaw stable salad dressing with edible oil comprising more than about 5 percent and less than about 35 percent of the dressing also emphasizes the use of a freeze-resistant starch. Wintersdorff, in U.S. Pat. No. 3,676,157, claims a spoonable (thick) salad dressing containing about 30 percent to about 70 percent edible oil with improved freeze-stability by the incorportion of a Xanthomonas hydrophilic colloid in a specific procedural process.
The foregoing is a summary of the prior art on certain essentials in the production of freeze resistant mayonnaise, and emulsified salad dressings and dressings. More recently there has been an increasing demand for freeze-thaw stable emulsified salad dressings. This has resulted from the significant increase in away-from-home eating in restaurants, particularly fast-food outlets. Institutional feeding is another growth factor in the demand-market structure. Another factor in demand is the growing delicatessen market. These markets are making demands on convenience foods and food ingredients, including emulsified salad dressings for the preparation of salads and sandwich spreads, particularly those containing ham, chicken, and tuna.
Changing patterns of marketing and distribution have emphasized the need for dressings with even greater freeze-thaw stability as exemplified by stability or emulsion integrity after numerous freeze-thaw cycles. In addition, the need for dressings with resistance to mechanical stress has become apparent. Such stress occurs through the "spooning" and mixing of the thawed dressing. It is not unusual to see a dressing which appears uniform after quiescent thawing, but which breaks down with liberation of oil on mixing. This has not been particularly addressed in the prior art.